SIMPLE TECHNICAL TRICKY INTERVIEW QUESTIONS.
Will HA & DRS work when Vcenter is down ?
HA(High Availability
),DRS(Distributed Resource scheduler)
HA will work, because there is an
HA agent running on each host, and the hosts monitor each other and keep lists
of running VMs that need to be restarted in case of a host failure. vCenter is
just used to (de-)activate and configure HA.
DRS will NOTwork without vCenter,
because vMotion recommendations are computed by the vCenter service, and it
also initiates the migration processes.
LUN Basics:
What is LUN and how does it simplifies our life.
In simple terms, a logical unit number (LUN) is a slice or portion of a configured set of disks that is presentable to a host and mounted as a volume within the OS.
Internal architecture and front end connections aside, the primary reason for purchasing a disk array is to provide data storage capacity through presenting a number of physical disks, and making them available and configurable to the IT administrator for the purposes of distributing portions of that capacity (e.g. volumes) to specific applications.
The disks in an array are usually configured into smaller sets (RAID groups) to provide protection against failure. These RAID groups define the manner in which the group of physical disks handle data when it is written to the disks within that group (and as such, the way in which that data is protected). However, a RAID group (being the underlying structure of that group of physical disks), is not presentable to the host. In order to do this, an administrator must create a LUN which can be presented to and mounted on a host operating system.
In terms of LUN management, the LUN can either be configured as a small ‘slice’ of the total usable capacity of the RAID group, or configured to use the total space available within that RAID group, (dependant on the requirements of the application that it wishes to use it). The logical unit number (LUN), when presented to the host, shows as a mountable volume of the same capacity as the ‘slice’ configured by the administrator, hiding any remaining capacity on that RAID group. Any remaining capacity can then be 'sliced' into additional logical unit number (LUNs) as required
Note : LUN 0 is a front-end communications device. You cannot present/unpresent LUN 0 to a host as an end-user.
Regarding Maximum its rare but few good interviewer ask this question to know your hold on basics knowledge 5.1
Maximum
Virtual machines per host 512
Hosts per vCenter Server 1000
Powered-on virtual machines per vCenter Server 10000.
Registered virtual machines per vCenter Server 15000.
Basic Requirements for HA
2 Host should be there at least.
Host should have static I.P
1 or 2 management network/Vm kernel network port.
Access to datastore from both the host.
VM Tools should be installed for VM Monitoring.
Basic requirement for DRS to be functional
Shared storage should be there.
Shared VMFS Volume.
Processor should be of same vendor and same generation
Vmotion should happen between the host.
When Interviewer ask
Wwhat is DRS (Distributed Resource Scheduler ) ?
He don’t want to know the
full form so
Be crisp in the reply and then tell him about the 3 modes and
how the placement happens.
(Distributed Resource Scheduler) is a utility that balances computing
workloads with available resources in a virtualized environment.
Mode
Manual
Partially
Automatic
Automatic
Initial
Placement
Manual
Automatic
Automatic
Dynamic
Load Balancing
Manual
Manual
Automatic
HA will work, because there is an
HA agent running on each host, and the hosts monitor each other and keep lists
of running VMs that need to be restarted in case of a host failure. vCenter is
just used to (de-)activate and configure HA.
DRS will NOTwork without vCenter,
because vMotion recommendations are computed by the vCenter service, and it
also initiates the migration processes.
LUN Basics:
In simple terms, a logical unit number (LUN) is a slice or portion of a configured set of disks that is presentable to a host and mounted as a volume within the OS.
Internal architecture and front end connections aside, the primary reason for purchasing a disk array is to provide data storage capacity through presenting a number of physical disks, and making them available and configurable to the IT administrator for the purposes of distributing portions of that capacity (e.g. volumes) to specific applications.
The disks in an array are usually configured into smaller sets (RAID groups) to provide protection against failure. These RAID groups define the manner in which the group of physical disks handle data when it is written to the disks within that group (and as such, the way in which that data is protected). However, a RAID group (being the underlying structure of that group of physical disks), is not presentable to the host. In order to do this, an administrator must create a LUN which can be presented to and mounted on a host operating system.
In terms of LUN management, the LUN can either be configured as a small ‘slice’ of the total usable capacity of the RAID group, or configured to use the total space available within that RAID group, (dependant on the requirements of the application that it wishes to use it). The logical unit number (LUN), when presented to the host, shows as a mountable volume of the same capacity as the ‘slice’ configured by the administrator, hiding any remaining capacity on that RAID group. Any remaining capacity can then be 'sliced' into additional logical unit number (LUNs) as required
Note : LUN 0 is a front-end communications device. You cannot present/unpresent LUN 0 to a host as an end-user.
Regarding Maximum its rare but few good interviewer ask this question to know your hold on basics knowledge 5.1
Basic Requirements for HA
LUN Basics:
What is LUN and how does it simplifies our life.
In simple terms, a logical unit number (LUN) is a slice or portion of a configured set of disks that is presentable to a host and mounted as a volume within the OS.
Internal architecture and front end connections aside, the primary reason for purchasing a disk array is to provide data storage capacity through presenting a number of physical disks, and making them available and configurable to the IT administrator for the purposes of distributing portions of that capacity (e.g. volumes) to specific applications.
The disks in an array are usually configured into smaller sets (RAID groups) to provide protection against failure. These RAID groups define the manner in which the group of physical disks handle data when it is written to the disks within that group (and as such, the way in which that data is protected). However, a RAID group (being the underlying structure of that group of physical disks), is not presentable to the host. In order to do this, an administrator must create a LUN which can be presented to and mounted on a host operating system.
In terms of LUN management, the LUN can either be configured as a small ‘slice’ of the total usable capacity of the RAID group, or configured to use the total space available within that RAID group, (dependant on the requirements of the application that it wishes to use it). The logical unit number (LUN), when presented to the host, shows as a mountable volume of the same capacity as the ‘slice’ configured by the administrator, hiding any remaining capacity on that RAID group. Any remaining capacity can then be 'sliced' into additional logical unit number (LUNs) as required
Note : LUN 0 is a front-end communications device. You cannot present/unpresent LUN 0 to a host as an end-user.
Regarding Maximum its rare but few good interviewer ask this question to know your hold on basics knowledge 5.1
Maximum
Virtual machines per host 512
Hosts per vCenter Server 1000
Powered-on virtual machines per vCenter Server 10000.
Registered virtual machines per vCenter Server 15000.
Basic Requirements for HA
2 Host should be there at least.
Host should have static I.P
1 or 2 management network/Vm kernel network port.
Access to datastore from both the host.
VM Tools should be installed for VM Monitoring.
Basic requirement for DRS to be functional
Basic requirement for DRS to be functional
Shared storage should be there.
Shared VMFS Volume.
Processor should be of same vendor and same generation
Vmotion should happen between the host.
When Interviewer ask
Wwhat is DRS (Distributed Resource Scheduler ) ?
He don’t want to know the
full form so
Be crisp in the reply and then tell him about the 3 modes and
how the placement happens.
(Distributed Resource Scheduler) is a utility that balances computing
workloads with available resources in a virtualized environment.
Mode
|
Manual
|
Partially
Automatic
|
Automatic
|
Initial
Placement
|
Manual
|
Automatic
|
Automatic
|
Dynamic
Load Balancing
|
Manual
|
Manual
|
Automatic
|
In case the interviewer doesn't seems to be convinced or you miss points while
Dedicated infra for individual business units
Reduction
of cooling costs.
Requirements for FT (Fault Tolerence )to be enabled and
functional.
The VM on which FT is going to be
enabled should have single processor.
How many DNS records are there
Zone DNS database is a collection of resource records and
each of the records provides information about a specific object. A list of
most common records is provided below:
The text record can hold arbitrary non-formatted text string.
Typically, the record is used by Sender Policy Framework (SPF) to prevent fake emails to appear to be sent by you.
What is the difference between distributed switch and standard switch ?
Will update soon.........
Dedicated infra for individual business units
Centralized
control of hardware parameters
Continuous
monitoring of hardware utilization
Optimization
of the use of hardware resources as conditions change
Prioritization
of resources according to applications importance
Downtime-free
server maintenance
Optimization
of energy efficiency
Reduction
of cooling costs.
Requirements for FT (Fault Tolerence )to be enabled and
functional.
The VM on which FT is going to be
enabled should have single processor.
It should be in HA Cluster.
Maximum 4 FT VM can be there per host.
FT Vm kernel port group should be
configured.
BIOS Based power saving technology
should be disabled.
In FT VM`s memory reservation equal to
memory allocation.
Shared storage should be there.
Disk format should be thick eagered
zero.
How many DNS records are there
Zone DNS database is a collection of resource records and
each of the records provides information about a specific object. A list of
most common records is provided below:
Address Mapping records (A)
The record A specifies IP address (IPv4) for given host. A
records are used for conversion of domain names to corresponding IP addresses.
IP Version 6 Address records (AAAA)
The record AAAA (also quad-A record) specifies IPv6 address for
given host. So it works the same way as the A record and the difference is the
type of IP address.
Canonical Name records (CNAME)
The CNAME record specifies a domain name that has to be queried
in order to resolve the original DNS query. Therefore CNAME records are used
for creating aliases of domain names. CNAME records are truly useful when we
want to alias our domain to an external domain. In other cases we can remove
CNAME records and replace them with A records and even decrease performance
overhead.
Host Information records (HINFO)
HINFO records are used to acquire general information about a
host. The record specifies type of CPU and OS. The HINFO record data provides
the possibility to use operating system specific protocols when two hosts want
to communicate. For security reasons the HINFO records are not typically used
on public servers.
Note: Standard values in RFC 1010
Integrated Services Digital Network records (ISDN)
The ISDN resource record specifies ISDN address for a host. An
ISDN address is a telephone number that consists of a country code, a national
destination code, a ISDN Subscriber number and, optionally, a ISDN subaddress.
The function of the record is only variation of the A resource record function.
Mail exchanger record (MX)
The MX resource record specifies a mail exchange server for a
DNS domain name. The information is used by Simple Mail Transfer Protocol
(SMTP) to route emails to proper hosts. Typically, there are more than one mail
exchange server for a DNS domain and each of them have set priority.
Name Server records (NS)
The NS record specifies an authoritative name server for given
host.
Reverse-lookup Pointer records (PTR)
As opposed to forward DNS resolution (A and AAAA DNS records),
the PTR record is used to look up domain names based on an IP address.
Start of Authority records (SOA)
The record specifies core information about a DNS zone,
including the primary name server, the email of the domain administrator, the
domain serial number, and several timers relating to refreshing the zone.
Text records (TXT)
The text record can hold arbitrary non-formatted text string.
Typically, the record is used by Sender Policy Framework (SPF) to prevent fake emails to appear to be sent by you.
Will update soon.........
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